I'm not sure this counts if I go specifically by the notion that it is the same film re-released theatrically, but a very good nominee for most-released film on any format has to be Night Of The Living Dead. When it was first released, due to the credits being altered at the last minute for reasons which escape me at the moment, they neglected to place a copyright notice on the final print. This led to revival shows without payment to either the distributors or George A Romero. Later, when the video boom hit, it was released by various companies simultaneously, some with the copyright shown over the film, some without the copyright notice. By the late 80s this led to Tom Savini (FX guru of Dawn Of The Dead) directing a remake starring Patricia Tallman and Tony Todd. This was slightly altered from the original script, but wasn't as successful.
The early 00's (noughties? can anyone think of a better term?) the original was re-released on DVD (again, several companies competing) with the remake appearing on the shelves as well. One year's Halloween television output was notable for their being a showing of Night Of The Living Dead on various channels for over three continuous days (overlapping, so the full run of this insanity was even longer). There was talk of a further remake, but by this point in the sorry saga I had pretty much given up on keeping score of who was doing what with the film. And yes, the original is now available on BluRay, with cinema screenings still taking place occasionally...
Somehow it is fitting that I write this on the verge of Halloween rolling around again.